It is known in the prior art to build aluminum-hulled boats made from sheet aluminum. Since they are light, such boats have found great popularity for various aquatic activities, such as fishing and motorboating. Because of their light construction, aluminum boats typically need bulkheads and other cross-braces extending transversely between the opposing hull sides in order for the boats to be sufficiently rigid. In many boats, the cross-braces also serve as bench seats. These cross-braces are typically held in place by rivets projecting through holes in the thin-skinned hull below or close to the water line. Unfortunately, rivets are also potential leak sites. Because of the need to include the cross-braces and use many rivets, construction of such aluminum-hulled boats is labor intensive and the boats are consequently more expensive. The cross-braces also add weight to the boat. As such, it is not possible to make a light aluminum hull boat with an open hull design since cross-braces are required to achieve sufficient strength. As noted above, these cross-braces frequently take the form of bench seats, even in boat designs where several midships' bench seats are not desired and an open hull with a single swivel seat and console arrangement is preferred.
With conventional construction of aluminum boats, the requirement to add bench seats as cross-braces, and the mechanisms sometimes used to distribute the load placed on the seats to the hull bottom so as not to be all supported by the rivet points to the hull sides, render it infeasible to add an interior flat deck to the boat. The extra weight and the necessary riveting of floor supporting braces to the boat hull further deter the use of interior decking. As such, the user must walk on the curved interior side of the hull bottom, which is less comfortable and provides a less stable than desired platform on which to stand or place equipment.
While aluminum sheets used for boat hulls are relatively light, they also have a relatively high modulus of elasticity. Accordingly, trailerable aluminum-hulled boats frequently suffer permanent deformations to their hulls at the trailer support points. This is due to the stresses produced by the trailer supports applying large localized pressures against the hull. The problem is more severe the greater the weight of the hull and the more articles which are in or attached to the hull while being trailered, such as an outboard motor. The problem is compounded when the boat, after loaded on the trailer, is used to carry extra weight, such as fishing, camping and other sporting gear. As a result of the susceptibility to permanent deformation, aluminum boat manufactures recommend users never load their boats on trailers of the type where rollers support the boat hull. Although most modern trailers use rollers since they are more convenient and make boat loading easier and safer, the limited number of rollers used apply too great a concentration of force on the hull. Thus, aluminum boat owners are relegated to using the old style bunk trailers which support the boat hull on long, flat planks usually covered with a soft material.
Not only are hull deformations unsightly, but they lead to a decrease in operating efficiency due to the increased hull drag. In addition, flexing at these points of deformation can lead to hull failure and leakage through nearby rivet holes.
Another problem common to aluminum hull boats is the vibration, noise and general pounding of the water on the hull which is transferred to the boat occupants, thus making for a less enjoyable and more fatiguing boat ride.
While it is known in the prior art to use foams in certain boat constructions to provide additional flotation and to deaden sound, the low density foams used tend to deteriorate due to wave impact and vibration. As a result, these low density foams are not recommended for use in hulls of planing boats.